Process for preparing beta-phenylethyl alcohol

ABSTRACT

B-PHENYLETHYL ALCOHOL SUITABLE FOR PERFUMERY USE IS PREPARED IN EXCELLENT YIELDS BY THE HYDROGENATION OF STYRENE OXIDE IN THE PRESENCE OF THE TWO CATALYSTS: RANEY NICKEL AND PALLADIUM, AND FRACTIONALLY DISTILLING THE ALCOHOL.

United States Patent 3,579,593 PROCESS FOR PREPARING BETA-PHENYLETHYLALCOHOL Thomas F. Wood, Wayne, N.J., assignor to Givaudan Corporation,Clifton, NJ. No Drawing. Eled Apr. 18, 1968, Ser. No. 722,224 Int. Cl.C07c 29/00 U.S. Cl. 260-618 6 Claims ABSTRACT OF THE DISCLOSUREB-Phenylethyl alcohol suitable for perfumery use is prepared inexcellent yields by the hydrogenation of styrene oxide in the presenceof the two catalysts: Raney nickel and palladium, and fractionallydistilling the alcohol. I

SUMMARY OF THE INVENTION This invention relates to a process forpreparing fi-phenylethyl alcohol of perfume grade, in excellent yields,by hydrogenating styrene oxide in the presence of two specificcatalysts: Raney nickel and palladium. These catalysts do not give thedesired results when employed by themselves; nor do mixtures of othercatalysts.

BACKGROUND OF THE INVENTION B-Phenylethyl alcohol is widely used inflavors and perfumery. It even has been said that, perhaps, no roseperfume is ever compounded without it.

As will be readily understood, therefore, efforts to devise practical,commercial, synthetic methods for its preparation have been numerous.One of such methods is the one disclosed in US. Pat. No. 2,524,096, bythe present inventor, and involves the catalytic hydrogenation ofstyrene oxide in the presence of low temperature hydrogenationcatalysts. While the method covered by US. Pat. 2,524,096 has attainedconsiderable commercial success, it still has certain drawbacks.Considerable amounts of solvents are required for best yields,necessitating a time-consuming and expensive distillation step forremoval of the solvents. Also, undesirable ethyl benzene, while obtainedin lower amounts than was the case prior to the development of themethod of US. Pat. 2,524,096, nevertheless, are still formed insubstantial amounts. Ethyl benzene is undesirable because of itsdisagreeable odor and because its presence reduces the water solubilityof fi-phenylethyl alcohol to such an extent that the latter does notpass the standard test for perfume-grade acceptance. The test referredto is the requirement that 2 ml. of B-phenylethyl alcohol must beclearly soluble in 100 ml. of water.

Attempts have been made to improve the basic liquid phase processdisclosed in US. Pat. 2,524,096, but without substantial success. Forexample, US. Pat. 2,822,403 suggests conducting the catalytichydrogenation of styrene oxide in a water suspension and recommends theuse of an emulifying or dispensing agent to achieve an intimate mixtureof styrene oxide and water. The patent gives no actual weight yields butasserts in one example an almost quantitative yield and in the otherexample a 99% yield.

Aside from the fact that the present applicant has only been able tosecure yields up to about 85%, the process of US. Pat. 2,822,403 has thedisadvantages that it involves 1) a costly and time-consumingdistillation to remove the large amounts of water; and (2) a costlysolvent extraction or salting-out procedure necessitated by the presenceof an emulsifying agent. Further, it has been found that large amountsof the undesirable ethyl benzene are formed in accordance with theprocess of US. Pat. 2,822,403.

3,579,593 Patented May 18, 1971 In general, the procedure of U8. Pat.2,524,096 may be followed in conducting the process of this invention.Thus, styrene oxide in the liquid phase is hydrogenated at comparativelylow temperatures and superatmospheric pressure, in the presence ofcatalyst. The catalyst employed here is unique, however, being, asaforesaid a combination of nickel and palladium. Small amounts of polarsolvents, inert under the reaction conditions, are also employed in thereaction mixture. Lower aliphatic alcohols having up to 5 carbon atoms,such as methanol, ethanol and isopropyl alcohol, are preferred. Also, asis known, small amounts of alkaline materials can be used to suppressisomerization of styrene oxide to phenylacetaldehyde.

The individual catalysts which form the components of the catalyticmixture used herein are well-known hydrogenation catalysts. They may becombined into a mixture of catalysts prior to use or may be separatelycharged into the reaction vessel.

The palladium may be used as such, and may, for example, be formed insitu. It is presently preferred, for practical and economic reasons, touse finely divided palladium deposited on an inert or active carrier,such as active carbon, kieselguhr, barium carbonate, barium sulfate,calcium carbonate, aluminum oxide, etc. The palladium content of suchPd-carrier combinations may vary. I have found that available mixtureshaving Pd contents of 1% and 5%, by weight, are satisfactory. Ipresently prefer to use palladium in the form of palladium on activecarbon, the palladium content of the commercial products being 1 and 5by weight. If desired, the palladium on carbon catalyst may be speciallyprepared, for example, in accordance with the procedure set forth inOrganic Synthesis, collective volume III, 385-6, 686-7.

Raney nickel catalyst is the presently-preferred form of nickel catalystused in accordance with this invention.

The proportions of the nickel and palladium catalyst employed inaccordance with the present process may vary over wide limits.

Amounts of nickel from about 1 to 10 parts, by weight, based on the 100parts by weight of styrene oxide charged into the reaction vessel givesatisfactory results. From about 3 to 6 parts by weight, on the samebasis, are preferred.

As to the palladium catalyst, from about 0.0001 to 0.1 part, by weightof the metal, on the same basis, i.e., per 100 parts by weight of thestyrene oxide used, can be employed, from about 0.003 to 0.006 part byweight being preferred.

The beneficial eflFects flowing from the use of nickel and palladium,jointly, as catalysts, were unexpected. Neither catalyst alone givesthese effects, each one resulting in undesirable byproducts andappreciably lower yields of ,B-phenylethyl alcohol. For example, a yieldof about 10% of ethyl benzene accompanies the use of nickel alone;whereas as much as 11% of phenylacetaldehyde is obtained when thecatalyst used is palladium on carbon.

-Nor do mixtures of other catalysts give the advantageous resultsobtained by the joint use of nickel and palladium catalysts.

For example, when copper chromite catalyst (commercial grade) issubstituted for Raney nickel in the process of this invention, there isobtained under the best conditions an yield of fi-phenylethyl alcoholwhich is unacceptable to perfumers because of a by-odor similar tophenylacetaldehyde. Even after redistillation the product is notsatisfactory for perfumery use. A mixture of ruthenium on carbon (5%)with palladium on carbon (5%) gives poor results. A mixture of Raneynickel and platinum on carbon (5%) in the hydrogenation process gives acrude product similar in all respects to that obtained with Raney nickelcatalyst alone. This crude contains to 11% of ethylbenzene and is thusnot suitable for producing perfumery grade B-phenylethyl alcohol bydirect distillation.

Another unexpected feature of the process of this invention is theexcellent results secured even when very small amounts of solvents areused. Such amounts are as low as 5 to percent by weight of the styreneoxide. Of course, if desired, much larger amounts may be used. Thesmall, minor amounts of solvents used in the preferred form of thisprocess permit the obtaining of perfumery-grade fi-phenylethyl alcoholdirectly from the crude hydrogenation product by filtration, to removecatalysts, followed by vacuum distillation, there being no need to stripoff solvents or to wash impurities out or to resort to any otherpurification technique.

In conducting the present process, it will be understood vy chemiststhat equimolecular amounts of hydrogen and styrene oxide are required toconvert the latter to ,8-

phenylethyl alcohol. An excess of hydrogen, e.g., 1.1 mols of the latterto 1 mol of styrene oxide is advantageous.

Nor are the temperature and pressure conditions, under which thereaction is conducted, critical. Temperatures within the range fromabout 10 C. to 140 C. are satisfactory, temperatures from about C. to110 C. being presently preferred. Pressures from about 50 to 500 poundsper square inch may be used, pressures from 50 to 200 psi. beingpreferred.

Especially advantageous results are obtained when the reaction isconducted in two stages. The first stage involves the use of relativelylow temperatures and pressures, e.g., temperatures from about 10 C. to60 C., preferably 30 to C., and pressures around psi. Then when hydrogenabsorption substaintially ceases under the first stage conditions, thetemperature and pressure are raised to enable the theoretical amount ofhydrogen to be absorbed. The second stage temperatures may be from about90 C. to 140 C., preferably about 90 C. to 110 C.; and the pressuresduring this stage may be around 200 p.s.i.

In order more fully to illustrate this invention, the following exampleis given. It is understood that this example is given for purposes ofillustration and not for purposes of limitation.

All parts are by weight and all degrees are in degrees centigrade,unless otherwise specified.

EXAMPLE I (a) Two hundred and forty grams of pure styrene oxide wascharged into the 500 ml. stainless steel bomb of an autoclave along with28 g. of 85% methanol (aqueous), 2 g. of sodium bicarbonate, 10 g. ofRaney nickel. catalyst and 1 g. of palladium on carbon (1% catalyst. Theautoclave was evacuated and hydrogen was introduced up to a pressure of50 p.s.i. The temperature was increased to 30 and agitation was begun.The temperature was allowed to rise to 40 and hydrogen was continueduntil absorption stopped (2 hrs.) and close to the theoretical amount ofhydrogen had been absorbed.

The temperature was then increased to 100 and the pressure of hydrogenwas raised to 200 psi. and agitation was continued for 2 hrs. longer.The batch was cooled, removed from the autoclave, filtered, anddistilled at 1 mm. Hg pressure.

There was obtained 232 g. of pure B-phenylethyl alcohol, B.P. 6869 (1mm.) r1 1.5332, free of ethylbenzene and suitable for perfumery use.This material was soluble to the extent of 2 ml. in 100 ml. of waterproducing a clear solution. The yield was 96.6% based on styrene oxide.

(b) When the above procedure of part (a) was repeated omitting thepalladium catalyst, using instead 1 g. of active carbon, and the Raneynickel, the yield was only 212 g. of fl-phenylcthyl alcohol (88.3%yield) and the product was unacceptable for perfumery use because itcontained traces of ethylbenzene and failed to pass both odor andwater-solubility requirements. Vapor-phase chromatography showed thatthe original crude from the autoclave contained about 10% ofethylbenzene.

(c) When the hydrogenation was carried out as in (a) above except thatboth palladium metal catalyst and active carbon were omitted, only Raneynickel being used, the crude from the autoclave contained 10% ofethylbenzene and the yield of fl-phenylethyl alcohol was 209 g. (87.0%yield). The product was unacceptable for perfurnery use for the samereasons as in (b) above.

(d) When the hydrogenation was carried out as in (a) above except that5% palladium on active carbon (1 g.) was substituted for the 1%palladium on active carbon, there was obtained 230 g. of purefl-phenylethyl alcohol (96% yield) suitable for erfumery use withoutfurther processing.

(c) When the hydrogenation was carried out as in (a) above except that5% platinum on active carbon (1 g.) was substituted for the 1% palladiumon active carbon, there was obtained a crude which contained 10.6% ofethylbenzene and gave 211 g. of distilled fl-phenylethyl alcohol (88%yield). This was not suitable for perfumery use and failed both the odorand water-solubility tests because of the presence of a small amount ofethylbenzene.

(f) When the hydrogenation was carried out as in (a) above except that50 mg. of Palladium Black (finely divided palladium metal withoutcarrier) was substituted for the 1% palladium on active carbon, therewas obtained 219 g. of pure distilled B-phenylethyl alcohol suitable forperfumery use without further processing.

EXAMPLE II (a) One hundred and twenty grams of pure styrene oxide wascharged into the 500 ml. stainless steel bomb of an autoclave along with160 g. of methanol, 5 g. of Raney nickel catalyst, and 0.5 g. ofpalladium on carbon (5%) catalyst. After evacuation of the autoclavehydrogen was introduced up to a pressure of 50 p.s.i. Hydrogenation wasconducted at room temperature with agitation until the absorptionstopped (2 hrs.) and close to the theoretical amount of hydrogen hadbeen taken up. The temperature was then increased to 70 and the batchstirred under hydrogen at 50 p.s.i. for 3.5 hrs. The batch was cooled,removed from the autoclave, filtered, distilled for removal of methanol,and vaccum-distilled at 1 mm. Hg pressure. There was obtained 113 ofpure B-phenylethyl alcohol (94.3%) free of ethylbenzene and suitable forperfumery use.

(b) When the hydrogenation of styrene oxide was carried out as in (a)above except that the recovered catalyst mixture from (a) was used,there was obtained 116 g. of pure fi-phenylethyl alcohol (96.7%), freeof ethylbenzene and suitable for perfumery use.

The foregoing illustrates the practice of this invention, which,however, is not to be limited thereby but is to be construed as broadlyas ermissible in view of the prior art and limited solely by theappended claims.

What is claimed is:

1. In a process for preparing beta-phenylethyl alcohol by the catalytichydrogenation of styrene oxide, the improvement which comprisesconducting the hydrogenation in the presence of Raney nickel andpalladium catalysts, wherein the amount of Raney nickel employed is fromabout 1 to 10 parts, and the amount of palladium employed is from about0.001 to 0.1 part based on parts of styrene oxide, all of the partsbeing by weight, and the reaction is conducted at temperatures withinthe range from about 10 C. to C. and under pressures of from about 50 to500 pounds per square inch.

2. A process in accordance with claim 1, wherein the palladium isdeposited on active carbon.

3. A process in accordance with claim 1, wherein the reaction isconducted in the presence of a minor amount of an inert, polar solvent.

4. A process in accordance with claim 1, wherein 240 grams of styreneoxide, 28 grams of aqueous methanol, 2 grams of sodium bicarbonate,grams of Raney nickel and 1 gram of a 1 percent mixture of palladium oncarbon are charged to an autoclave and hydrogen gas is introduced up toa pressure of 50 p.s.i., the temperature of the reaction contents beingwithin the range from about 30 C. to C. and when hydrogen absorptionceases increasing the temperature to 100 C. and the pressure of thehydrogen gas to 200 p.s.i. continuing the reaction until hydrogenabsorption ceased again, filtering and removing perfumery-grade,B-phenylethyl alcohol by distilling the filtrate.

5-. A process in accordance with claim 1, wherein the reaction isconducted in two stages, the first stage being conducted at temperatureswithin the range from about 10 C. to C., under a pressure of about 50p.s.i. until hydrogen absorption ceases, and the second stage beingconducted at temperatures within the range from about C. to C., underpressure of about 200 p.s.i.

6. A process in accordance with claim 5, wherein an inert, polar solventis also employed.

References Cited UNITED STATES PATENTS OTHER REFERENCES Newman et al.:JACS 71 (1949), 3362-3363.

BERNARD HELFIN, Primary Examiner US. Cl. X.R. 252522

